A series of firings and feuds initiated by Defense Secretary Pete Hegseth has left the Army essentially rudderless as it struggles to deal with the threat posed by cheap, deadly drones and missiles that have pounded U.S. bases in the Middle East. The Army has not had a chief of staff, the service's top officer, since Mr. Hegseth fired Gen. Randy George without explanation in April, and there are no signs that he is close to filling the position, said current and former officials speaking on the condition of anonymity to discuss sensitive personnel matters.